Thermal compensator for hydraulic systems



Feb. 17, 1948. A E, KREMlLLER 2,436,009 I THERMAL COMPENSATOR FOR HYDRAULIC SYSTEMS Filed Sept. 14, 1943 2 Sheets-Sheet l Feb- 17, 1948 A. E. KREMILLER .A 2,436,009

THERMAL COMPENSATOR FOR IQIYDRAULIC SYSTEMS Filed Sept. 14, 1945 2 Sheens--Sheecl 2 3m I ASW/vw? E WMM/LER ating the accumulator piston unit.' However; when tl 1e system is not under operation the spring loaded compensator pressurizes the system and the pressure on both sides of the valve members 3u of the two one-way restrictor valves is the same. The light springs 33 now hold thevalve members of these units seated. Any thermal expansion or contraction ow. ofythe iiuid in the system is relatively slow and will leak through these valves suiiiciently to allow the4 compensator piston unit to be moved whereby the compensator acts to displace or receive uid so that the proper volume of iiuid is maintained throughout the system regardless of temperature changes.

With reference to Fig. 1, it is seen that -pump or transmitter unit D is provided with a by-pass around the piston 4I and controlled `by a needle valve 42 thereby permitting of synchronization of the system as is customary in this art. Figs. 1 and 4 show the motor or slave -unit E as provided with bleeder valves 43 and 44 .on opposite sides of the piston 45 therein. -These valves are unscrewed to open opposite ends of the cylinder 46 to the atmosphere whereby air may be bled from .the system and if desired the system maybe filled by removing these valves and introducing the thus provided.

Y As here shown (see Figs. 1` and 4) the motor or slave unit E is provided with a hydraulic? locking means generally4 designated VL `to Aprevent externally applied loads o n the slave unit from affecting the system, valso lock the slave unit and-vv mechanism controlled thereby against any uncle sired or unintentional movement from positions gained responsive to-actuationof the system.v

livered thereto from the lines B and C. A valve-l operating piston 54 is reciprocable in a cylinder` bore-55 in the Wall of cylinder 4B. This cylinder bore is common to the valves 41 and 48- andarranged so .that the piston 54 will move responsive to fluid -entering the cylinder fromeither of the'lines B and "C. The piston 54 has projections 56 and 51 on opposite ends for engaging and unseating the valves 41 and 48. The cylindrical passages 49 Vand 50 are diametrically reduced at 491: and 59m.

When fluid under pressure derived from the unit D enters the cylinder bore 55 in unit E, for example, through line C, it unseats valve 41 and enters the left end oi the cylinder 46 and moves the piston 45 to the right. At the same time.'

the valve-operating piston 54 moves to the right and the projection 51 thereon engages and unseats the valve 48 thereby allowing a return flow of fluid from cylinder 46 to unit D through the other line B. Upon cessation of operation of unit D, the springs 53 close the valves 41 and 48, the spring for valve 48 then returning the piston 54 to the neutral position shown in Figs. 1 and 4. As the valves 41 and 48 are now seated, the slave unit piston P is hydraulically locked against movement as a result of any externally applied load on the slave unit.

When working nuid is delivered to the slave unit through `the line B the valve 48 is'opened byl the pressure; of the fluid and the valve-oper.- atingpiston54 ismoved to the left thereby open-v ing the l,valve 41.l The main piston 45 now moves to Athe .left and in all other respects the slave. unit D foperatesin the same manner as pre-, viously described upon cessation of vthis lreverse operation of the pump unitD.

' It is now apparent that while the system is under operation the flow of fluid to the compensator is `;sorestricted by the one-way restrictor valves of my improved compensator unit A as to: render the `action of this unit practically negligible. However, when the system is static, that is, not under operation, the force of the spring L in the compensator unit A is keffective to mainfluid through the one of the ports..

tain the system under pressure and compensate for expansion and contraction of the fluid and iiuid lines inthe manner hereinbefore set forth, whereby the systemy is maintained incondition to be fully and instantly responsive to the manual operation ofthe transmitter or pump unit,

without the objections which have been presentin closed, remote control, dual line systems as heretofore used and which have not had the beneiit of my improved dual-cylinder-dual-piston compensator embodying the features of construction andr operation described and illustrated,l herewith.-

. '5 Inorder to obtain the necessary precise re-v4 sponse and continued accurate positioning of the motor or slave unit E to the operation of the transmitter or pump unit D, it is necessary that there be no' by-pass connection lof any kind (even of a greatly restricted character) between the; conduits VB and C. Therefore it is necessary toprovide the compensator unit A with the two chambers 2 and 3 eachof which is connected with one only of the two power transmitting.Y conoluits.-y Y Y While 'I have shown and described a specific embodiment of my invention I do not limit myself tothe exact details of construction set forth, and the invention embraces such changes,.

modifications and equivalents `of the parts and.,

leading into said bores, a dual piston unit sepa.V

rating the bores in said housing and lhaving connected and coaxial piston portions movable ini said bores vtoward and away from said'ports, and

means insaidr housing forj urging said piston" portions toward said ports and maintaining vunder pressure .riiuid contained insaid bores be-- twee'n ysaid piston portions `and vsaid ports, vsaid pistonA unit being hollowV and receiving a portion of said means in the hollow thereof.

2. In a compensator for a dual fluid line hydraulic system, a housing closed at its ends and having coaxial cylinder bores one of which is of greater diameter than the other, means aiording the communication of said bores with the uid lines of the system including ports located adjacent corresponding ends of said bores, a dual piston unit separating the bores in said housing and having connected and coaxial piston portions movable in said bores toward and away from said ports, means in said housing for urging said pis.

having coaxial cylinder hores` one-ot? which is or! greatery diameterfthan the othenmeans afford-- ingI the communication. of fsaidlv bores-withf the iiuid lines of thezsystem-including ports-located adjacent correspondingends-lofsaid bores', a'dualpiston unit separatingftheboresfin said housing and `having connected andeoaxial-piston.portions A movable inl said bores toward -and-fawaydromports, a springinterposedbetweensaid pis-` tong-unit`-and an endof said housing-forlurging' lsaid piston v`portionstoward said .portslandm'aimtaining under pressure Vfluid contained in said bores betweensaid piston vportions andsaid ports,-

said pistonY unit beinghollow and receiving a -por tionofsaid springin the hollow--thereof, a `rod iii-said rhollow of the piston and extending from-- the` piston -unit `out through .said endofffsaidhousing-and a head on the innerend ofsaid rod engaging the head of the pistonunlt interiorly of the latter, said spring surrounding said rodand having oneendrest'ed against the headv on said rod;

" 4. In a-compensator fora-dual fluid line ahy'A draulic system, a housing. closed at its 4endsvandv havingcoaxial oylinderj'bores loneoif-wlfuch is Off greater diameterthan the otherymeans afford-` ing the communication f of said bores with the ilild lines ofthe systemincluding ports located adjacentcorresponding endsof said'bores, a ydualp'iston unit separating the horesv in' said housing and having connected and coaxial piston-'porf tions movable 'in said boresvtoward and 'away from said ports, and rmeans in Y said' housing for urging'said pistonportions toward said ports and maintaining nnder-pressuretluid contained iiisaid bores between-said piston portions and 45 said ports, said bores-having substantially equal iluid capacityfbetweensaid l corresponding ends and the piston portions therein, whereby given increments of piston movement'` effect Yequal volumetricidisplacement of uid fronieach of said housing bores.

5. In a compensator for a dualiluid line hy'- draulic system, a housing closedlatlgits ends l. and having coaxial cylinder bores one of which is off greater diameter than the other, means aioi'd ing-the communicationfof said bores withftheY nuid lines-of the system including ports leading. into saidbores, a dual piston `vunit:separating theA boresinsaid housing and having connected and.

coaxial-pistonportions movable 'in said boresfw,yqmnber` toward .and away from said ports, means interposed :between said piston unitsandA anend of said housingfior urging said `.piston portions;

Number Name Date Re;19,4,32" Carroll' Jan. 22, 1935'. n 372;;674 Greene Dec. 27, 1887' 60? 1,707,781' Blanchard Apr. 2, 1929 137861912 Madden Dec. 30, 193i)y 1,911,634 Madden May 30, l1933.v 2,098,653 Carroll Nov. 9, 1937 2,148,268l Kerr Feb. 21, 1939 65 2,188;913x- Masteller Feb.` 6, 1940- 2,192,175 Ballard Mar. 5, 1940 2,308,043 Brown Jan.r 12,1943

FCREIGN PATENTS Country Date 519,9991' Great Britain 1----.. Mar. 15, 1940'` France Nov. 8 1934- marasme-peris- Aand:mamai-ning under' prs# sure -iiudcontained in said-bores Vbetween-said piston :portions and,saidports,4 and means associated i withsa-id portsv4 for rendering the piston unitsubstantially unresponsive to the pressure oithef-working fluid-inthe system whenthe latter iseunderfoperation and which allows a compensating-nowofa-fludthrough said ports and'renf dersthe-dual piston-unit responsive to such com-- havingcoaxialcylinder bores-one of which is of I greaterdiaxneter than the-other, means aii'ordingwthe communication of said bores with the iluidlines of the system includingvports leading into said`bores,a dual piston unit separating the bores-insaid housing and having connected andv towardand awayfrom said ports, means interposed between Isaid pistonunitand an endv ofL b'elngehollow `and receiving aportion of lsaidV piston -urgingmeans in the hollow thereof, and arodinsaid'hollowof i the I piston and Aextending fromfthe piston unitout through said end of said Housing; -sald piston u urging means surrounding said rod and being operatively related-thereto in; such a manner as to cause thepiston and rod to move in unison-r The following references are of'record in the` Y nie of this patent:

' UNITED STATES PATENTS coaxialfpiston portions movable in said boresl 

